After made of polyethylene terephthalate, or polyester that contains polyethylene terephthalate as a main component has a high melting point, a high modulus of elasticity, excellent heat resistance and excellent chemical resistance, and thus is used widely for curtains, rugs, clothes, blankets, cloths for sheets, table covers, cloths for covering chairs, wall materials, artificial hairs, interior materials for cars, exterior reinforcing materials, safety nets and the like.
For hair products such as hairpieces, hair wigs, crepe hairs, headbands and doll hairs, human hairs, artificial hairs (modacrylic fibers and polyvinyl chloride fibers) and the like have been used conventionally. However, supplies of human hairs have been difficult, and the importance of artificial hairs has risen. Modacrylic fibers have been used frequently as artificial hair materials by utilizing its flame-retardant property, but they are insufficient in the point of its heat-resistible temperature. Recently, an artificial hair fiber using a fiber that contains polyester represented by polyethylene terephthalate as a main component, which has excellent heat resistance, has been suggested.
However, for using a polyester-based fiber as an artificial hair material, flame retardancy is necessary in the light of safety. Since conventional polyester-based fibers are flammable, improving flame retardancy of polyester fibers has been tried in various ways, for example, a method for making a fiber of polyester that is copolymerized with a flame-retardant monomer containing a phosphorus atom, a method for allowing a polyester fiber to contain a flame retardancy agent and the like are known.
As the method for copolymerizing the said flame-retardant monomer, for example, a method for copolymerizing a phosphorus compound that has a phosphorus atom serving as a cyclic factor and has excellent thermostability (Patent Document 1), a method for copolymerizing a carboxy phosphinic acid (Patent Document 2), a method for blending or copolymerizing a phosphorus compound with polyester that contains polyarylate (Patent Document 2) and the like are suggested. As the application of the flame retardancy technique to an artificial hair, for example, a polyester fiber that is copolymerized with a phosphorus compound (Patent Document 4) is suggested. However, since an artificial hair requires high flame resistance, for using the copolymerized polyester fiber for the artificial hair, its polymerization amount needs to be increased, and as a result, heat resistance of the polyester is decreased significantly, whereby melt spinning is made difficult. Moreover, in the case where a flame is close thereto, ignition or burning does not occur, but there is another problem in that melting or dripping occurs.
As the latter method for including the flame retardancy agent, a method for allowing a polyester fiber to contain fine particles of a halogenated cycloalkane compound (Patent Document 5), a method for including bromine atom-containing alkylcyclohexane (Patent Document 6) and the like are suggested. The method for allowing the polyester fiber to contain the flame retardancy agent has a problem in that a containing temperature is required to be as high as 150° C. or more in order to obtain sufficient heat resistance, a containing processing time is required to be long, or a large amount of a flame retardancy agent is required to be used, thereby causing problems such as a decrease of a fiber property, a decrease of productivity and an increase of a manufacturing cost.
On the other hand, the improvement of the flame retardancy by adding an antimony compound as a flame-retardant aid is suggested (Patent Documents 7 and 8), but in the case of performing it for a fiber, there occurs problems in that spin processibility is unstable due to a decrease of a melt viscosity, and filament breakage occurs due to the antimony particles and the like.
By the way, for the antimony compound that is used conventionally as the flame-retardant aid, for example, antimony trioxide having an average particle diameter ranging from about 0.5 μm to about 1 μm has been used widely, in the light of dispersibility, uniformity of the flame retardancy, availability and the like. However, antimony trioxide having an average particle diameter ranging from 0.4 μm to 1.0 μm has a high concealing power, and in the case of using the antimony trioxide having the particle diameter in the above-described range, a hue of the obtained filament is degraded (whitened), and transparency tends to be decreased. Moreover, in the case where the average particle diameter of the antimony trioxide is less than 0.4 μm, and in particular, less than 0.1 μm, the concealing power thereof is decreased, and the decrease of the hue becomes small, but aggregation is likely to occur, so that it is difficult to disperse uniformly without the aggregation. In the case where the aggregation occurs, it is possible that the filament breakage occurs, and non-uniform of the flame retardancy occurs.
Moreover, in the case of using the polyester-based fiber as an artificial hair, various silicone-based finishing agents (polyorganosiloxane-based fiber treating agents) are used generally in order to provide flexibility, smoothness and the like. For example, as the polyorganosiloxane-based fiber treating agent for providing flexibility, wrinkle resistance, elasticity and compression recovery, polydimethyl siloxane, polymethyl hydrogen siloxane, polydimethylsiloxane having hydroxyl groups at both ends, vinyl group-containing polyorganosiloxane, epoxy group-containing polyorganosiloxane, amino group-containing polyorganosiloxane, ester group-containing polyorganosiloxane, polyoxyalkylene-containing polyorganosiloxane and the like axe exemplified.
Moreover, as the polyorganosiloxane-based fiber treating agent, treating agents made of combinations with alkoxysilane and/or polyacrylamide resin and a catalyst, and the like also are known.
For example, a method by using a treating agent that includes: polyorganosiloxane that contains at least two epoxy groups in one molecule; and polyorganosiloxane that contains an amino group (Patent Document 9), a method by using a treating agent that includes: polyorganosiloxane having hydroxyl groups at both ends; polyorganosiloxane containing an amino group and an alkoxy group in one molecule; and/or partial hydrolysate and condensate thereof (Patent Document 10) are disclosed.
Moreover, a treating agent that includes: polyorganosiloxane containing an epoxy group; and aminoalkyltrialkoxy silane (Patent Documents 11 and 12), and diorganopolysiloxane having triorganosiloxy groups at both ends that contains two or more amino groups in one molecule (Patent Document 13) are described. Other than these, a method by using a treating agent that includes: aminopolysiloxane containing two or more amino groups in one molecule; and alkoxysilane that contains one or more reactive group such as an amino group and an epoxy group (Patent Document 14) is suggested.
However, the polyester-based fibers to which these silicone-based finishing agents (polyorganosiloxane-based fiber treating agents) are added have improved smoothness, combing smoothness and the like, but since the silicone-based fiber treating agents themselves are flammable, there remains problems in that flammability of the non-flame-retardant synthetic fibers is promoted and flame retardancy of the flame-retardant synthetic fibers also is decreased significantly.
As described above, under the present circumstances, the flame-retardant polyester-based artificial hair that maintains its fiber properties such as heat resistance and strength/elongation of the conventional polyester fibers, and has excellent settability, touch feeling, combing smoothness, transparency and processing stability has not been obtained yet.    Patent document 1: JP 55 (1980)-41610 B    Patent document 2: JP 53 (1978)-13479 B    Patent document 3: JP 11 (1999)-124732 A    Patent document 4: JP 3 (1991)-27105 A    Patent document 5: JP 3 (1991)-57990 B    Patent document 6: JP 1 (1989)-24913 B    Patent document 7: Japanese Patent No. 2693331    Patent document 8: JP 2002-128998 A    Patent document 9: JP 43 (1968)-17514 B    Patent document 10: JP 53 (1978)-36079 B    Patent document 11: JP 53 (1978)-197159 B    Patent document 12: JP 53 (1978)-19716 B    Patent document 13: JP 53 (1978)-98499 B    Patent document 14: JP 58 (1983)-17310 B